Inflammatory cell recruitment to the central nervous system (CNS) is a cardinal feature of numerous pathological processes, including multiple sclerosis (MS). Despite recent progress, the soluble signals that attract inflammatory cells from perivascular accumulations into the CNS parenchyma remain obscure. The present proposal derives from experience in our laboratories and is based on the hypothesis that a specific class of chemoattractant cytokines termed 'chemokines' is synthesized by astrocytes in response to inflammatory stimuli; we propose that astrocyte-derived chemokines in turn function to recruit inflammatory cells into the CNS parenchyma. This hypothesis will be addressed by performance of two Specific Aims: Al. We will establish the relationship between chemokine gene expression and CNS inflammation in informative model systems. Three models will be studied, each with specific advantages: 1) EAE of SJL/J mice actively immunized with proteolipid protein (PLP) encephalitogens; 2) EAE of Lewis rats, after adoptive transfer of myelin basic protein (MBP)-specific or myelin oligodendroglial glycoprotein (MOG)-specific T-cell lines; 3) Traumatic brain injury in neonatal and adult mice. We will assess chemokine transcript levels by a sensitive, semi-quantitative reverse transcription/polymerase chain reaction (RT/PCR) assay. Subsequently, we will establish the relationship between specific histopathologic alterations and localized chemokine production in CNS tissues, assayed by in situ hybridization (ISH). A2. We will evaluate regulation of chemokine gene expression in astrocytic cells in vitro and murine CNS in vivo. Our preliminary work showed that CNS expression of chemokine mRNAs was limited to astrocytes in mice with EAE. To determine the mechanism of this chemokine gene expression, we will address the cytokine regulators of IP-10 and JE/MCP-l transcription in human astrocytic and monocytic cells in vitro and in murine CNS cells in vivo: 1) Regulation of chemokine gene expression in human astrocytic and monocytic cells will be compared. 2) Chemokine gene expression in the murine CNS will be determined by RT/PCR and ISH in vivo after intravenous injection of pro-inflammatory cytokines IFNgamma and TNFalpha. The production of chemoattractant cytokines by astrocytes provides insight into the role of endogenous neural cells in amplifying inflammatory processes. Research proposed here will enhance our understanding of varied pathologic processes and suggest potential therapeutic strategies for disorders limited to the CNS.